A Critical Warning message in AFT Arrow

Full message is:

Junction X uses normal or standard flow units like Y in a flow path with dynamic gas mixing. Flows cannot be calculated accurately unless GSC module is used.

When standard flowrates (like scfm) or normal flowrates (like Nm3/hr) are used as flow demands and the model has dynamic gas mixing, the “standard” or “normal” density cannot be obtained because there is no certain gas mixture at the required flow rate. Without a standard/normal density then the flowrate cannot be converted into a true mass flowrate.

The user should either change the model to use known pressures (like Assigned Pressures or Tanks) or use the GSC module to obtain the desired flowrate.